The utilization of tamperproof container-closure packages, in which the closure is of a thermoplastic material, is receiving wide acceptability in the market place. Such packages will become even more market dominant upon acceptance by the carbonated beverage industry of the use of thermoplastic closures. One such closure is shown in U.S. Pat. No. 4,206,851. This type of closure has an annular tamperproof band disposed downwardly from the bottommost extent of the closure sidewall. The band has at least one frangible area. Attachment to the closure sidewall by the band is achieved by the utilization of a plurality of spaced-apart non-frangible ribs. The container to which this type of closure is to be fitted has an annular flange beneath the thread portion of the container neck. With the closure fitted to the container, the position of the tamperproof band is such that it is disposed, for the most part, at a position lower than the container annular flange. With the closure so fitted, heat is then applied to the closure band so that it shrinks to a position of interference underneath the container flange. Removal of the closure from the container is by unthreading which results in upward axial movement of the closure. Since the tamperproof band is in an interfering fit with the annular container flange, its axial movement is prevented unless rupture of the band occurs. By providing the frangible areas in the band, such rupturing does occur and is the visible indication that the package has been tampered with.
Another type of tamperproof system which uses thermoplastic closures is the one in which there is provided a tamperproof band which is attached to the lowermost extent of the closure sidewall by a plurality of frangible ribs. The band itself has no frangible areas. The closure and the container will both have configurations which coact together to lock the band to the container when the closure is rotated to achieve its removal from the container. For example, one particularly popular system utilizes a container having a set of projections which coact with an annular array of teeth which are found on the tamperproof band. The teeth and projections do not coact with one another when the closure is applied to the container, however, when the closure is torqued for removal, the teeth and projections coact in an interfering manner which prevents the entire closure from rotating. Raising the removal torque in the closure results in fracturing of the ribs and thus separation of the band from the remainder of the closure. The closure can now be rotated to achieve removal. This separation of the band from the closure gives visual indication to the consumer that tampering has occurred.
While the two before-described systems are viable, each has a drawback. The first-described system, which utilizes a heat shrinking technique to obtain interference between the tamperproof band and the annular container flange, is disadvantaged in the heat shrinking technique is relatively expensive equipment wise and cycle time wise. The other described tamperproof system is disadvantageous in that the tamperproof band, after it has been separated from the remainder of the closure, is free to fall from the container neck. As can be appreciated, this characteristic can result in a nuisance for the consumer as attempts to pour the contents from the container will also tend to deposit the separated tamperproof band into the same receptacle in which the container contents are being poured.
Therefore, it is an object of this invention to provide a high fidelity tamperproof system for use with thermoplastic closures which is inexpensive for the packager and which makes possible the permanent capture of the tamperproof band to the container.